The influence of lower limb plyometric and resistance training on the stiffness of Achilles and patellar tendons in recreational athletes

Myotonometry and extended field-of-view ultrasound imaging allow reliable quantification of patellar tendon stiffness and length at rest and during maximal load, whereas several restrictions exist for the Achilles tendon

Introduction

Stiffness and length are well-established tendon parameters in sports and medicine. Myotonometry and ultrasound imaging are the commonly used methods to quantify these parameters. However, further studies are needed to clarify the reliability of these methods, especially when assessing maximally loaded tendons and when conducted by different experienced investigators. This study aimed to determine the intra- and interrater reliabilities of measuring the stiffness and length of the patellar tendon (PT) and Achilles tendon (AT) using the myotonometry method and the extended field-of-view ultrasound (EFOV-US) technique at rest and maximal load performed by different experienced investigators.

Methods

Twenty-seven participants were examined on three different days by one experienced investigator and one novice investigator. Primary outcomes were the intraclass correlation coefficient (ICC) and associated 95% confidence interval (95% CI), coefficient of variation (CV), standard error of measurement (SEM), and minimal detectable change (MDC) across the measurement days and investigators.

Results

For PT measurements at rest and maximal load, the estimated ICCs for stiffness and length were ≥.867 and ≥.970, respectively, with 95% CIs ranging from poor (.306) to excellent (.973) and good (.897) to excellent (.999). The CV, SEM, and MDC for PT stiffness and length were ≤5.2% and ≤2.0%, ≤39.3 N/m and ≤0.9 mm, and ≤108.9 N/m and ≤2.6 mm, respectively. For AT measurements, some restrictions were evident for stiffness at rest and both parameters at maximal load. However, regarding AT length at rest, the estimated ICC was ≥.996, with an excellent 95% CI (.987-.999). The CV, SEM, and MDC for AT length at rest were 2.8%, ≤1.1 mm, and ≤2.9 mm, respectively.

Conclusion

The estimated ICCs show good to excellent reliability for the myotonometry method and the EFOV-US technique for measuring PT stiffness and length at rest and maximal load for experienced and novice investigators. However, some restrictions are evident for the AT, especially for measurements at maximal load.

INFLUENCES OF ECCENTRIC CONTRACTION TRAINING ON SOCCER PLAYER'S SPEED

ABSTRACT Introduction: Strength quality can be divided into maximum strength, rapid strength, endurance, and reaction strength. Rapid strength has been a hot topic of discussion in contemporary sports industry research. Objective: Study the influences of eccentric contraction training of the lower limbs in soccer players and its repercussions on the athletes’ speed. Methods: A multifunctional centrifugal training instrument was used as a training tool through the experimental method to analyze the effect of eccentric contraction training on the rapid strength of soccer players. The athletes were divided into experimental and control groups for training. Explosive power, speed sensitivity, and dynamic index of special rapid power were tested before and after training. Results: Compared to the control group, the explosive power index, the sensitivity index, and the kinetic index showed better expressivities in the experimental group; the four jumping ability indexes, the three sensitivity indexes - except the 15s step frequency - and the eccentric training in the experimental group showed a very significant improvement (P<0.01). Conclusion: Eccentric contraction training can effectively improve muscle strength; its training effect is better than that of concentric training, especially eccentric contraction training on the lower limbs, which has an important impact on the rapid strength of soccer players. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

CHANGES IN LOWER LIMB BONE DENSITY IN YOUNG JUMPERS

ABSTRACT Introduction The research on the exercise effect on the human bone density and skeletal muscle content mainly focuses on the middle-aged and elderly population. However, few studies on different sports’ effects upon bone and muscle density in college students and adolescents. Objective Study the effect of physical training on bone density and lower limb jumping ability in young people. Methods The relationship between bone mineral density and lower limb jumping ability was analyzed by mathematical statistics. Male individuals aged 10-20 years were divided into the early adolescence group (n=26) and late adolescence group (n=37). According to training status, they were divided into preadolescent athletic group (n=11), non-athletic group (n=15); puberty athletic group (n=11) and non-athletic group (n=15). The following indicators were used: bone density, vertical jump test, continuous vertical jump test, RDJ index. Results Athletes’ bone mineral density (BMD) is related to their muscle strength. These results suggest a certain internal connection between the (BMD) of bone tissue and the development of muscle strength. Therefore, there is evidence of differences in lower limb bone mineral density and jumping ability between the two groups. Conclusion Bone mineral density in the lower limbs of adolescents is correlated with jumping ability. Exercise can help improve bone density in adolescents. Evidence level II; Therapeutic Studies - Investigating the results.

Changes in Tissue Composition and Load Response After Transtibial Amputation Indicate Biomechanical Adaptation

Despite the potential for biomechanical conditioning with prosthetic use, the soft tissues of residual limbs following lower-limb amputation are vulnerable to damage. Imaging studies revealing morphological changes in these soft tissues have not distinguished between superficial and intramuscular adipose distribution, despite the recognition that intramuscular fat levels indicate reduced tolerance to mechanical loading. Furthermore, it is unclear how these changes may alter tissue tone and stiffness, which are key features in prosthetic socket design. This study was designed to compare the morphology and biomechanical response of limb tissues to mechanical loading in individuals with and without transtibial amputation, using magnetic resonance imaging in combination with tissue structural stiffness. The results revealed higher adipose infiltrating muscle in residual limbs than in intact limbs (residual: median 2.5% (range 0.2–8.9%); contralateral: 1.7% (0.1–5.1%); control: 0.9% (0.4–1.3%)), indicating muscle atrophy and adaptation post-amputation. The intramuscular adipose content correlated negatively with daily socket use, although there was no association with time post-amputation. Residual limbs were significantly stiffer than intact limbs at the patellar tendon site, which plays a key role in load transfer across the limb-prosthesis interface. The tissue changes following amputation have relevance in the clinical understanding of prosthetic socket design variables and soft tissue damage risk in this vulnerable group.